000
AXPZ20 KNHC 210949
TWDEP 

TROPICAL WEATHER DISCUSSION                                      
NWS NATIONAL HURRICANE CENTER MIAMI FL                         
1005 UTC SUN SEP 21 2014

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS 
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND 
METEOROLOGICAL ANALYSIS.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0945 UTC.

...SPECIAL FEATURES...
 
TROPICAL STORM POLO LOCATED NEAR 21.6N 110.5W OR ABOUT 100 MILES 
S-SW OF THE SOUTHERN TIP OF BAJA CALIFORNIA PENINSULA AT AT 0900 
UTC SEP 21. THE MINIMUM CENTRAL PRESSURE IS ESTIMATED AT 1004 
MB. POLO IS MOVING W OR 285 DEG AT 06 KT...AND IS EXPECTED TO 
CONTINUE ON THIS TRACK THROUGH MON. MAXIMUM SUSTAINED WINDS ARE 
CURRENTLY ARE AT 35 KT WITH GUSTS TO 45 KT.  

STRONG NE WIND SHEAR IS EXPOSING THE CENTER WELL TO THE SE OF A 
CLUSTER OF SCATTERED MODERATE ISOLATED STRONG WITHIN 60 NM OF 
21.5N111.5W. SCATTERED MODERATE CONVECTION IS ALSO NOTED WITHIN 
45 NM OF 23N113W. POLO MAY STILL PRODUCE RAINFALL AMOUNTS OF 1 
TO 2 INCHES ACROSS THE SOUTHERN BAJA CALIFORNIA PENINSULA TODAY.

SWELLS GENERATED BY POLO WILL AFFECT PORTIONS OF THE SOUTHERN 
BAJA CALIFORNIA PENINSULA OVER THE NEXT FEW DAYS. THESE SWELLS 
CAN CONTRIBUTE TO THE GENERATION OF LIFE THREATENING SURF AND 
RIP CURRENT CONDITIONS. SEE THE LATEST PUBLIC ADVISORY UNDER 
AWIPS/WMO HEADERS MIATCPEP2/WTPZ32 KNHC AND FORECAST ADVISORY 
UNDER HEADERS MIATCMEP2/WTPZ22 KNHC FOR ADDITIONAL DETAILS. 

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
           
THE MONSOON TROUGH EXTENDS W ACROSS PANAMA AND COSTA RICA  
BETWEEN 09-10N TO THE PACIFIC COAST OF COSTA RICA AT 10N85W... 
CONTINUES NW TO 11N98W THEN SW TO 07N113W WHERE IT LOSES 
IDENTITY. SCATTEROMETER WINDS INDICATE THE MONSOON TROUGH 
RESUMES NEAR 15N120W AND CONTINUES SW TO BEYOND 12N140W. 
SCATTERED MODERATE ISOLATED STRONG CONVECTION IS OBSERVED WITHIN 
150 NM EITHER SIDE OF A LINE FROM 06N77W TO 10N95W TO 07N111W.

SCATTERED MODERATE ISOLATED STRONG CONVECTION IS ALSO OBSERVED  
OVER AND WITHIN 180 NM W OF THE COAST OF CENTRAL AMERICA AND 
MEXICO FROM 86-102W.

LOW PRESSURE IS EXPECTED TO GRADUALLY DEVELOP ALONG THE MONSOON 
TROUGH NEAR 12N95W OVER THE NEXT COUPLE OF DAYS WITH A 1007 MB 
SURFACE LOW...POSSIBLY TROPICAL CYCLONE...EXPECTED ON TUE 
EVENING. THIS LOW SHOULD TRACK W ALONG THE MONSOON TROUGH WITH 
SW FLOW INCREASING TO 20-25 KT OVER THE SE SEMICIRCLE LATE THU. 

...DISCUSSION...                                                 
A 1017 MB HIGH PRESSURE IS QUASI-STATIONARY NEAR 27N137W WITH 
ITS ANTICYCLONIC ENVELOPE DOMINATING THE MARINE AREA W OF 120W 
AND TO THE N OF THE MONSOON TROUGH WITH GENERALLY NE-E 10-15 KT 
TRADES ACROSS THE TROPICS W OF 120W. A WEAK COLD FRONT WILL MOVE 
INTO THE FAR NW WATERS LATE TONIGHT. THE FRONT WILL INITIALLY BE 
ACCOMPANIED BY ONLY A SW-W-WNW 10 KT WIND SHIFT. THE WEAK FRONT 
WILL REACH FROM 32N134W TO 26N137W LATE TUE. A SECONDARY 
NORTHWESTERLY 15 KT SURGE WILL PUSH THE FRONT E TO A POSITION 
FROM 32N128W TO 25N140W LATE WED WITH NW WINDS INCREASING TO 15 
KT W OF THE FRONT. ADDITIONALLY...NW SWELLS W OF THE FRONT WILL 
MIX WITH LONG PERIOD SE SWELL...RESULTING IN SEAS BUILDING 8-12 
FT ACROSS THE WATERS NW OF THE FRONT...WITH THE MAXIMUM SEAS 
ALONG 31N. THE FRONT WILL REACH FROM 32N117W TO 22N140W LATE THU 
WHERE IT WILL LOSE IDENTITY...BUT NW WINDS WILL INCREASE TO 15-
20 KT ALONG THE PACIFIC COAST OF THE BAJA PENINSULA TO THE N OF 
26N...WITH SEAS BUILDING 6-9 FT IN MIXING NW AND SE SWELL 
WITHIN THIS AREA ON FRI.       

$$
NELSON